1. Field of the Disclosure
The present disclosure relates generally to apparatus and methods for formation fluid collection and testing.
2. Description of the Related Art
During both drilling of a wellbore and after drilling, clean fluid from the formation is often extracted to determine the nature of the hydrocarbons in hydrocarbon-bearing formations. Fluid samples are often collected in sample chambers and the collected samples are tested to determine various properties of the extracted formation fluid. To drill a well, drilling fluid is circulated under pressure greater than the pressure of the formation in which the well is drilled. The drilling fluid invades into the formation surrounding the wellbore to varying depths, referred to as the invaded zone, which contaminates the original fluid present in the invaded zone. To collect samples of the original fluid present in the formation, a formation testing tool is conveyed into the wellbore. A pump typically extracts the fluid from the formation via a sealed probe placed against the inside wall of the wellbore. The initially extracted fluid is discarded into the wellbore while testing it for contamination. When the extracted fluid is sufficiently clean, samples are collected in chambers for further analysis. Single and concentric probes have been proposed for extracting formation fluid. In concentric probes, separate pumps are used to extract fluid from the formation via an outer probe and an inner probe. The outer probe extracts the fluid present around the inner probe, which aids in removing the contaminated fluid more efficiently and may prevent fluid from the wellbore to flow into the inner probe. When the contamination is at an acceptable level, the fluid from the inner probe is pumped into sample chambers (also referred to as “sampling”), while the fluid from the outer probe is discharged into the wellbore. During drawdown, the pump used for the outer probe creates pressure kick-backs in the inner probe, which reduces efficiency of the collection of the fluid samples. Also, since one pump is used for sampling the process of collecting samples can take long time.
The disclosure herein provides a formation evaluation system with a fluid extraction system that utilizes two or more probes that addresses some of the above-noted discrepancies.